Add better error code if WHVP is not enabled

[gamozolabs]

When running currently without WHVP enabled you get the following:

C:\dev\applepie\bochservisor_test>..\bochs_build\bochs.exe -q -f bochsrc.bxrc
========================================================================
                     Bochs x86 Emulator 2.6.9.svn
              Built from SVN snapshot after release 2.6.9
                  Compiled on Jan  8 2019 at 08:31:57
========================================================================
00000000000i[      ] reading configuration from bochsrc.bxrc
00000000000i[      ] installing win32 module as the Bochs GUI
00000000000i[      ] using log file bochsout.txt
Registering handler for a0000 bffff
Registering handler for e0000000 e0ffffff
Registering handler for fed00000 fed003ff
Registering handler for fec00000 fec00fff
Creating hypervisor!
thread '<unnamed>' panicked at 'WHvCreatePartition() error: 0xc0351000', src\whvp.rs:435:9
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

We could clean up this error code with something more specific.

[gamozolabs]

Done